CD19 expression is detected in very few myeloma cells by flow cytometry, although single molecule-sensitive direct stochastic optical reconstruction microscopy (dSTORM) demonstrated CD19 expression on a fraction of myeloma cells (10%–80%) in approximately 70% (n = 14) of MM patients with density of 13–5000 molecules/cell. This evidence concerns the gene CD19 and Miyoshi myopathy.